CVE-2026-59727 Astro: Cross-site scripting via unescaped transition:* directive values on hydrated islands
Attackers can inject arbitrary JavaScript via unescaped transition directives in Astro if developers pass untrusted input to them.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-59727?
CVE-2026-59727 is a low-severity cross-site scripting vulnerability in withastro astro, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Astro is a web framework for content-driven websites. In versions 3.10.0 through 7.0.3, when a transition:persist, transition:scope, or transition:persist-props directive is applied to a client-hydrated (client:*) component, Astro copied the directive value onto the rendered <astro-island> element without HTML-escaping it. If a developer reflects attacker-controlled input into one of these directives, an attacker can break out of the attribute and inject arbitrary HTML/JavaScript into the server-rendered output, resulting in reflected cross-site scripting (XSS). Exploitation requires the application developer to have written a non-idiomatic pattern — passing untrusted, request-derived input directly into a transition directive. Astro applications that do not route untrusted input into these directives are unaffected. This issue has been fixed in version 7.0.4.
Which versions are affected by CVE-2026-59727?
2 open source packages ship an affected version, including astro.
| Package | Affected | Fixed in |
|---|---|---|
astro npm | From 3.10.0 | 7.0.4 |
astro npm | From 3.10.0 | 7.0.4 |
How do I fix CVE-2026-59727?
Upgrade astro to 7.0.4 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-59727 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59727 exists.
Sources
Also known as GHSA-7pw4-f3q4-r2p2.